Crosslinked polymer materials have been studied and used in various applications due to superior mechanical properties, thermal stability, solvent resistance, etc. However, because the crosslinked polymer materials are sensitive to unexpected mechanical damage caused by continued force and external impact, they have limited life span in recycling.
In order to solve this problem, the development of self-healing polymer materials is drawing attentions as a new technology. Self-healing polymers can be largely classified into 1) extrinsic self-healing polymers and 2) intrinsic self-healing polymers. The extrinsic self-healing polymers self-heal by a healing additive injected directly thereinto, whereas the intrinsic self-healing polymers self-heal through chemical bonding.
In particular, regarding the preparation of intrinsic self-healing polymers, the Diels-Alder reaction whereby crosslinkages are formed reversibly depending on temperature. Many self-healing polymer materials have been proposed through theses and patents and self-healing polymers using the organic-inorganic hybrid material polysilsesquioxane have also been studied a lot.
However, the existing self-healing polymer materials require a process of blending dienes and dienophiles for the Diels-Alder reaction, which renders problems in compatibility and uniformity on a nanoscale level. In addition, they have the problems of nonuniform film surface, low transparency, imperfect crosslinkage and inability of recycling.